1. Field of the Invention
The present invention relates in general to a hybrid exchange for exchanging the STM (Synchronous Transfer Mode) data of narrow band calls such as voice data and the ATM (Asynchronous Transfer Mode) data of broad band calls and, more specifically to a hybrid exchange for exchanging the STM data in unit of each STM data by periodically transmitting this data using the STM time slot, an exchange for exchanging a plurality of STM data composite in unit of each STM data by periodically transmitting the data using the STM time slot and a re-arrangement method for STM data in exchange for re-arranging the STM data among a plurality of fixed length packets.
2. Description of the Related Art
FIG. 1 is a diagram showing an STM exchange for exchanging the STM data such as voice data. In the bTM exchange, the STM data which is periodically assigned to the time slot appearing on the frame in the predetermined period is exchanged in every time slot depending on the preset information For example, in FIG. 1, for the input line 1, A is assigned periodically to the time slot TS1, while B to the time slot TS2 and C to the time slot TS3. In the same manner, a, b, c are respectively assigned to each time slot in regard to the input line 2. Depending on the preset information, the STM data A assigned to the time slot TS1 on the input line 1, for example, is exchanged to the time slot TS2 of the output line 2. As explained above, the exchange system in the STM exchange is suitable for the communication for periodically sending information such as voice data.
However, on the occasion of dealing with the communication for sending the information generated like a burst signal with the STM exchange, an idle area is generated in the time slot to be periodically assigned and thereby transmission efficiency may be deteriorated.
Therefore, for the data which is generated like a burst signal in the data terminal, etc., a packet exchange system has been proposed to realize exchange of data by using a packet of the variable lengths and then adding a header indicating the destination address to the packet. However, the packet exchange requires the time for exchanging one packet because it executes the exchange process by analyzing destination address of the header added to the packet. Accordingly, the packet exchange is not suitable for transmission of broad band data.
Considering the background as explained above, there is provided an ATM exchange system in which data is divided in unit of data of the fixed length; a header information is added to the divided data to generate ATM cells; these ATM cells are asynchronously transmitted and the ATM exchange executes the exchange process from the point of view of hardware depending on the value of header added to the ATM cell. According to the ATM exchange system, the data which is generated like a broad band burst signal may be transmitted as in the case of the dynamic image communication terminal.
FIG. 2 is a diagram showing a network in which the ATM exchange and STM exchange are used simultaneously. In FIG. 2, the ATM network 10 is composed of a plurality of ATM exchanges and transmits the data through the ATM cell which is the packet in the fixed length of 53 bytes. The ATM network 10 accommodates, on the one hand, ATM terminals X, Y for transmitting the ATM data and on the other hand, accommodates, STM exchanges 20, 30, via ATM interfaces 40, 50, to accommodate STM terminals a, b for transmitting the STM data.
The ATM data from the ATM terminal X is transmitted, for every generation of data, to the ATM network 10 through the payload of the ATM cell having the header H indicating the ATM terminal Y. The ATM network 10 transmits this ATM cell to the ATM terminal Y depending on the routing information of the header H.
Meanwhile, the STM data from the STM terminal a is superimposed on the time slots which are periodically assigned and then transmitted to the STM exchange 20. For example, when the STM terminal a is designed as a voice terminal of 64 Kbps, the STM data is transmitted through the time slot of 8 bits assigned in the period of 125 xcexcs. This STM data is processed first in the STM exchange and then transmitted to the ATM interface 40. The ATM interface is provided for transferring the data between the time slot and ATM cell with each other. The ATM interface 40 loads this ATM data, for transmission to the ATM network 10, to one byte of the payload of the ATM cell having the header directed to the STM exchange 30 accommodating the STM terminal b. The ATM network 10 transmits the ATM cell loading this STM data, without any discrimination from the ordinary ATM cell, depending on the routing information of the header H of the ATM cell. The ATM interface 50 extracts, upon reception of this ATM cell, the STM data from the predetermined position of the payload and then sends this ATM cell to the STM exchange 30 using the time slot periodically assigned. The STM exchange 30 executes the exchange process of the time slot and then sends the STM data to the STM terminal b of the destination address.
In the present situation, the greater part of the terminals is formed almost of the STM terminals such as telephone sets and ATM terminals are only introduced gradually by means of dynamic image communication terminals. Therefore, it will be very convenient when the ATM terminals which are gradually introduced can also be accommodated in the STM exchange as well as the STM terminals.
However, the STM exchange intrinsically introduces the synchronous transfer mode system for periodically assigning the time slot in unit of STM data to each STM terminal. For example, the telephone set of 64 Kbps is manufactured based on the hardware and software for exchanging and processing the data by assigning the time slot in unit of 8 bits for every other 125 xcexcs. Therefore, the STM exchange of the related art has a problem that it cannot execute the exchange process for the ATM cell in unit of 53 bytes in different exchange unit.
Meanwhile, the ATM exchange is designed on the basis of the hardware and software of the asynchronous transfer mode for transferring the data as required when data is generated as the ATM cell of 53 bytes. Accordingly, when it is required to manufacture the STM exchange and ATM exchange, it is impossible to use in common the hardware and software for the STM exchange and ATM exchange and thereby there rises a problem that manufacturing cost cannot be reduced.
It is an object of the present invention to reduce manufacturing cost and effectively develop the STM exchange and the ATM exchange by using common hardware and software for the basic configuration of the STM exchange and the ATM exchange.
It is another object of the present invention to provide a hybrid exchange for exchanging the STM data to be transmitted periodically to enable the data exchange in unit of the ATM data to be transmitted asynchronously.
Yet another object of the present invention is to provide a hybrid exchange for enabling transmission of STM data such as voice data through reduction of the transmission delay.
A further object of the present invention is to provide a hybrid exchange which is connected to an ATM exchange for transmitting the ATM data in the form of ATM cell in order to transmit and exchange the STM data of the STM time slot even with an ATM exchange.
Yet another object of the present invention is to provide an exchange which establishes reception sequence of the STM data for communication of the STM data via the ATM network including the ATM exchange.
Yet a further object of the present invention is to provide an exchange which enables efficient use of payload for transmission of a plurality of STM data in the form of the ATM cell of the payload composite.
These and other objects of the invention are attained by a hybrid exchange for exchanging periodically transmitted first data and second data through time-division slots of a fixed length which includes a first time slot and a second time slot, the hybrid exchange comprising first inserting means for periodically assigning said first time slot to said first data and inserting said first data to said first time slot with an identifier which indicates the first data; second inserting means for non-periodically assigning said second slot to said second data and inserting said second data to said second time slot with an identifier which indicates the second data; first extracting means for identifying said first time slot and extracting said first data from said first time slot; and second extracting means for identifying said second time slot with an identifier which indicates said second data and extracting said second data from said second time slot.
The objects of the present invention are also attained by a hybrid exchange for exchanging STM data and ATM data transmitted periodically through a time-division-multiplexed time slot of a fixed length, said time slot being formed of an STM time slot and an ATM time slot; and hybrid exchange comprising first inserting means for periodically assigning said STM time slot to the STM data and inserting said STM data to said STM time slot with an STM/ATM identifier indicating the STM data; second inserting means for non-periodically assigning said ATM time slot to the ATM data and inserting said ATM data to said ATM time slot with the STM/ATM identifier indicating the ATM data; first extracting means for identifying said STM time slot with said STM/ATM identifier and extracting said STM data from said STM time slot; and second extracting means for identifying said ATM time slot with said STM/ATM identifier and extracting said ATM data from said ATM time slot.
The objects of the present invention are also attained by a hybrid exchange according to claim 4, wherein said first inserting means inserts the STM/ATM identifier to the header of said fixed length packet and the fixed length packet obtained by multiplexing a plurality of STM data to the payload section, and said first extracting means extracts the STM data from the payload section of said fixed length packet. A hybrid exchange for exchanging a first fixed length packet for storing an STM data composition of a plurality of subscribers and a second fixed length packet for storing STM data of one subscriber to the payload of the fixed length packet, the hybrid exchange comprising an identifier setting means for setting an STM/ATM identifier indicating existence of the STM data to a header of the first fixed length packet and setting the STM/ATM identifier indicating existence of the ATM data to a header of the second fixed length packet; a sequence information setting means for setting a sequence information regarding a periodical sequence to the header of said first fixed length packet; a storing means for storing the sequence information in the header of the first fixed length packet and position information in payload of the first fixed length packet corresponding to each STM data; an identifying means for identifying the first and second fixed length packets depending on the STM/ATM identifier; an STM data exchanging means for exchanging the first fixed length packet on the basis of the sequence information and position information stored in said storing means; and an ATM data exchanging means for exchanging the second fixed length packet in unit of the ATM data.
The ATM exchange interface section may comprise means for setting a management information consisting of transmission sequence information of the ATM cells transmitted to the ATM exchange in the predetermined period and identifying information for identifying the self hybrid exchange to the ATM cell assembled from the first fixed length packet, and means for setting the receiving sequence of the ATM cells received within the predetermined period on the basis of the management information of the ATM cells.
The objects of the present invention are further attained by a method for re-arranging STM data in an exchange for transmitting and receiving a fixed length packet arranging a plurality of STM data in the payload of the fixed length packet depending on a destination in a header of the fixed length packet and switching such STM data in unit of the STM data arranged in the payload, the method comprising the steps of detecting a fixed length packet having the idle areas larger than a predetermined vale in the payload in a plurality of fixed length packet; judging whether or not the total value of the idle area of the payload in a plurality of fixed length packets detected in said detecting step is larger than the predetermined value; and re-arranging the STM data arranged in the payload of a plurality of the fixed length packets to eliminate the idle area in the payload when the total idle area in the payload of a plurality of fixed length packets is judged to be larger than the predetermined value in said judged step.